Query String

The query string is a part of a URL that contains data and parameters to be passed to a web server. It is typically located at the end of a URL and starts with a question mark (?), followed by key-value pairs separated by ampersands (&).

The values passed in the query string are available in the $_GET superglobal array. The keys of this array correspond to the names of the parameters in the query string, and the values are the corresponding values passed.

<?php

// https://www.example.com/index.php?x=1

print_r($_GET);
Array(
     [x] => 1
)

?>

Documentation

Related : Universal Resource Locator (URL), $_GET